CMP = Compare (8-Bits)
| Hex | Mnemonic | Cycles |
|---|---|---|
| 30 | CMP A, A | 8 |
| 31 | CMP A, B | 8 |
| 32 nn | CMP A, #nn | 8 |
| 33 | CMP A, [HL] | 8 |
| 34 nn | CMP A, [N+#nn] | 12 |
| 35 nn nn | CMP A, [#nnnn] | 16 |
| 36 | CMP A, [X] | 8 |
| 37 | CMP A, [Y] | 8 |
| DB nn nn | CMP [N+#nn], #nn | 16 |
| CE 30 ss | CMP A, [X+#ss] | 16 |
| CE 31 ss | CMP A, [Y+#ss] | 16 |
| CE 32 | CMP A, [X+L] | 16 |
| CE 33 | CMP A, [Y+L] | 16 |
| CE 34 | CMP [HL], A | 16 |
| CE 35 nn | CMP [HL], #nn | 20 |
| CE 36 | CMP [HL], [X] | 20 |
| CE 37 | CMP [HL], [Y] | 20 |
| CE BC nn | CMP B, #nn | 12 |
| CE BD nn | CMP L, #nn | 12 |
| CE BE nn | CMP H, #nn | 12 |
| CE BF nn | CMP N, #nn | 12 |
Execute
#nn = Immediate unsigned 8-Bits
#ss = Immediate signed 8-Bits
A = Register A
B = Register B
N = Register N
[N+#nn] = Memory: (I shl 16) or (N shl 8) or #nn
[HL] = Memory: (I shl 16) or HL
[X] = Memory: (XI shl 16) or X
[Y] = Memory: (YI shl 16) or Y
[#nnnn] = Memory: (I shl 16) or #nnnn
[X+#ss] = Memory: (XI shl 16) or (X + #ss)
[Y+#ss] = Memory: (YI shl 16) or (Y + #ss)
[X+L] = Memory: (XI shl 16) or (X + signed(L))
[Y+L] = Memory: (YI shl 16) or (Y + signed(L))
; CMP Sc2, Sc
;
; Sc2 = Source 2
; Sc = Source
(discarded) = Sc2 - Sc
Description
"8-Bits Source 2" subtracts with "8-Bits Source", result is discarded.
This instruction is used to compare values.
Conditions
Zero: Set when result is 0
Carry: Set when result is < 0
Overflow: Set when result overflow 8-bits signed range (< -128 OR > 127)
Sign: Set when bit 7 of the result is 1
Examples
; A = 0x55
CMP A, $80
; A = 0x55
; 0xD5 (0x55 - 0x80 = 0x(1)D4)
; F = (Zero=0):(Carry=0):(Overflow=1):(Sign=1)
; B = 0x31
; A = 0xCF
CMP A, B
; B = 0x31
; A = 0xCF
; 0x9E (0xCF - 0x31 = 0x(0)9E)
; F = (Zero=0):(Carry=0):(Overflow=0):(Sign=0)